to 10,000 amperes at the plate, passing there through copper
terminals \ in, square, kept cool by water circulation. The
current is very gradually applied, and very slowly shut off, by
means of a rheostatic switch.
The value of nickel steel for armour plates is shewn by the
following figures, which prove a saving in weight of 43*8 % for
equivalent resistance, over ordinary steel plates:
Kind of Plate.
Soft Steel .........
Compound Steel and Iron
All Steel .........
Chrome Steel is obtained by the addition of chromium to
steel having about -4% of carbon, and the resulting metal is
not only extremely hard, but is * self-hardening,5 that is, it only
needs to be cooled in a current of air after forging, to make it
suitable for metal-cutting tools or armour-piercing shells. For the
latter purpose the French Government use
while other analyses give
A 12 in. chrome-steel projectile has pierced a i6-in. armour
plate, while a chilled chrome-steel armour plate has received a